Resonator for damping acoustic frequencies in combustion systems by optimizing impingement holes and shell volume

ABSTRACT

A resonator in a combustor of a gas turbine comprises a flow sleeve defining an air path to provide air flow to a combustion chamber of the combustor, and one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 15/410,109, entitled “FLOW CONDITIONER TO REDUCE COMBUSTION DYNAMICSIN A COMBUSTION SYSTEM,” filed Jan. 19, 2017, and co-pending U.S. patentapplication Ser. No. ______, entitled “DEVICE TO CORRECT FLOWNON-UNIFORMITY WITHIN A COMBUSTION SYSTEM,” which are incorporatedherein by reference.

BACKGROUND

Combustors, such as those used in industrial gas turbines, for example,mix compressed air with fuel and expel high temperature, high pressuregas downstream. The energy stored in the gas is then converted to workas the high temperature, high pressure gas expands in a turbine, forexample, thereby turning a shaft to drive attached devices, such as anelectric generator to generate electricity.

As the air/fuel mixture combusts, the hot gas that is generated createsfluctuations in pressure. These pressure fluctuations at certainfrequencies (e.g., 1-1000 Hz) create acoustic pressures through thesystem. Accordingly, the combustion system is susceptible to High CycleFatigue (HCF) resulting from these combustion dynamics. The inability toaccount for the frequency of oscillation will jeopardize the structuralintegrity of the combustion system which may lead to a catastrophicfailure.

There are known ways of preventing the excitation of natural frequencywithin the system. Acoustic pressure fluctuations that can generatenatural frequencies may be reduced by redesigning the hardware, changingair splits, or adding external resonators to the system. However, inlarge applications such as an industrial gas turbine, for example, thiscan result in adding significant cost or reduction of the combustionsystem performance as extensive time for tests and modifications areneeded. Additionally, external resonators for this purpose can reducethe combustor performance as the resonator will need air for damping.The air will be taken away from combustion, thereby decreasing theefficiency of the combustion. Such may result in increased emissionlevels, metal temperature, and thermal stresses, all of which willaffect the life and performance of the structure of the system.

BRIEF SUMMARY

In one embodiment of the invention, a combustor of a gas turbinecomprises a combustion chamber in which mixture of air and fuel iscombusted, a flow sleeve defining an air path to provide air flow to thecombustion chamber, and one or more impingement holes disposed on theflow sleeve tuned to a damping frequency.

In another embodiment of the invention, a resonator in a combustor of agas turbine comprises a flow sleeve defining an air path to provide airflow to a combustion chamber of the combustor, and one or moreimpingement holes disposed on the flow sleeve tuned to a dampingfrequency.

In yet another embodiment, a method of damping acoustic frequencies in acombustor of a gas turbine comprises the steps of providing air flow toa combustion chamber through an air path defined by a flow sleeve toform an air and fuel mixture in the combustion chamber, combusting theair and fuel mixture in the combustion chamber, and generating at leastone damping frequency via one or more impingement holes disposed on theflow sleeve tuned to the at least one damping frequency to damp acousticfrequencies generated by the combusting.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a combustion system in an exemplary gas turbine, accordingto an example embodiment.

FIG. 2 shows a sectional view of a combustor, according to an exampleembodiment.

FIG. 3, shows a sectional view of a resonator, according to an exampleembodiment.

FIG. 4 shows a schematic diagram of a resonator, according to an exampleembodiment.

FIGS. 5A and 5B show exemplary shapes and sizes of an impingement hole,according to example embodiments.

FIG. 6 is a schematic diagram of a resonator, according to anotherexample embodiment.

DETAILED DESCRIPTION

Various embodiments of an acoustic resonator in a combustion system aredescribed. It is to be understood, however, that the followingexplanation is merely exemplary in describing the devices and methods ofthe present disclosure. Accordingly, any number of reasonable andforeseeable modifications, changes, and/or substitutions arecontemplated without departing from the spirit and scope of the presentdisclosure.

FIG. 1 shows combustor 10 according to an exemplary embodiment. Forpurposes of explanation only, the combustor 10 is shown in FIG. 1 asapplied to an industrial gas turbine 20. However, combustors of otherapplications may be applied without departing from the scope of thepresent invention. For purposes of explanation and consistency, likereference numbers are directed to like components in the figures.

As shown in FIG. 1, air to be supplied to the combustor 10 is receivedthrough air intake section 30 of the gas turbine 20 and is compressed incompression section 40. The compressed air is then supplied to headend50 through air path 60. The air is mixed with fuel and combusted at thetip of nozzles 70 and the resulting high temperature, high pressure gasis supplied downstream. In the exemplary embodiment shown in FIG. 1, theresulting gas is supplied to turbine section 80 where the energy of thegas is converted to work by turning shaft 90 connected to turbine blades95.

As can be seen in FIG. 1, the entire structure is connected to thecombustor 10 and therefore the acoustic frequencies caused by thegeneration of the gas resonates through the entire system. Therefore,controlling the generation of the acoustic frequencies will have alasting effect on the operation, performance, and longevity of theentire system. Impact of the frequency is not only limited tofrequencies that are resonating throughout the engine. The impact of thefrequency on the combustion system, which takes place mainly in thecombustor when high amplitude frequencies are generated, cause damage tothe combustor system. This will result in the necessity to power downthe engine to make repairs and thus loss of revenue. Another scenario iswhen an external damper is used on the combustor to reduce dynamics. Inthis case, the damper will most likely reduce the combustor performanceas resonators will require air to operate. This air will be taken awayfrom combustion resulting in higher emission and thus lower performance.Additionally, adding resonators will reduce the outage cycle due to highthermal stresses on the resonator.

FIG. 2 is a sectional view of an exemplary combustor 10. Combustor 10includes one or more fuel nozzles 70 in the headend 50. It is to beunderstood that there may be one or more combustors 10 in any given gasturbine. Liner 150 and transition piece 160 channels the resulting highpressure, hot gas towards the turbine section 80.

FIG. 3 is a sectional view of a resonator according to an exemplaryembodiment. As shown in FIG. 3, flow sleeve 100 is encased by shell 110forming shell volume 120. Flow sleeve 100 is formed around liner 150 andtransition piece 160 such that air flows in the space formed between theflow sleeve 100 and liner 150 and transition piece 160. Flow sleeve 100has formed thereon one or more impingement holes 130 through whichcompressed, relatively hot air flows. Accordingly, impingement holes 130and shell volume 120 forms a Helmholtz resonator (i.e., resonator 140).Utilizing the shell volume 120 and the impingement holes 130 as aHelmholtz resonator eliminates the need for designing an externalresonator that reduce the combustor performance by siphoning air flowthat would normally flow through the combustion system.

FIG. 4 is a schematic diagram of resonator 140 formed by the shellvolume 120 and impingement holes 130 according to an exemplaryembodiment. The shell volume 120 acts as a compliance or volume of aHelmholtz resonator whereas the impingement holes 130 simulate the neckof the Helmholtz resonator.

Resonator 140 can be optimized by adjusting the size, thickness, shape,and locations of the impingement holes 130. Impingement holes 130 on theflow sleeve 100 that forms resonator 140 can damp longitudinal waveswith wavelength that stretches to the air path location between flowsleeve 100 and liner 150 and flow sleeve 100 and transition piece 160.In particular, mid-range frequencies (e.g., between 20-200 Hz) may bedampened by utilizing existing hardware in the combustor 10 according tothe exemplary embodiment. However, other frequencies may be targetedwithout departing from the scope of the present invention. Further,multiple impingement holes 130 may be formed and designed to targetseveral frequencies at once.

Air flow that passes through the impingement holes 130 can be controlledto improve damping. For example, different sizes and shapes of theimpingement holes 130 may be used to target different frequencies withdifferent damping capabilities. FIGS. 5A and 5B show exemplary shapesand sizes of impingement hole 130. The size of hole 110 may be varied byadjusting diameter (D) and/or thickness (T). For instance, a cylindricalshape in FIG. 5A produces higher damping than a trapezoidal shape inFIG. 5B as the neck effective length increases. Further, changes in theangle of the trapezoid in FIG. 5B causes further shifts in the acousticfrequency. While only two exemplary shapes are shown in FIGS. 5A and 5B,other shapes may be used without departing from the scope of the presentinvention.

FIG. 6 is a schematic diagram of an exemplary embodiment of resonator140. Unstable frequencies can be damped by chaining impingement holes130 and 130′ having different diameter, thickness and/or shape, forexample. Additionally, impingement holes 130″ may be placed on or closeto an anti-node of the mode-shape of the targeted wave and itsfrequency.

Some of the advantages of the exemplary embodiments include: reductionof the combustion dynamics or pressure waves amplitude so the life ofhardware can be extended, reduced or eliminated combustion dynamics forfrequencies between 20-200 Hz and thus extending the life of thehardware, and utilization of existing hardware within the combustionsystem, thus eliminating the need to add external resonators for low tomid range frequencies or the need to change the design of the hardwareto minimize the effect of the combustion dynamics and to reduce theacoustic pressure fluctuation.

It will also be appreciated that this disclosure is not limited tocombustion systems in industrial gas turbines. For example, combustionsystems in aero gas turbines and gas turbines in general can alsorealize advantages of the present disclosure. Further, the shapes,sizes, and thicknesses of the impingement holes are not limited to thosedisclosed herein. For example, impingement holes in the shape of asquare, rectangle, triangle, and other polygonal structures, such aspentagon, hexagon, and octagon to name a few examples can also realizethe advantages of the present disclosure. Additionally, any combinationof impingement holes having different size, thickness, and shape may bechained together to adjust the frequency of the resonator withoutdeparting from the scope of the present invention.

The breadth and scope of the present disclosure should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.Moreover, the above advantages and features are provided in describedembodiments, but shall not limit the application of the claims toprocesses and structures accomplishing any or all of the aboveadvantages.

Additionally, the section headings herein are provided for consistencywith the suggestions under 37 CFR 1.77 or otherwise to provideorganizational cues. These headings shall not limit or characterize theinvention(s) set out in any claims that may issue from this disclosure.Further, a description of a technology in the “Background” is not to beconstrued as an admission that technology is prior art to anyinvention(s) in this disclosure. Neither is the “Brief Summary” to beconsidered as a characterization of the invention(s) set forth in theclaims found herein. Furthermore, any reference in this disclosure to“invention” in the singular should not be used to argue that there isonly a single point of novelty claimed in this disclosure. Multipleinventions may be set forth according to the limitations of the multipleclaims associated with this disclosure, and the claims accordinglydefine the invention(s), and their equivalents, that are protectedthereby. In all instances, the scope of the claims shall be consideredon their own merits in light of the specification, but should not beconstrained by the headings set forth herein.

What is claimed is:
 1. A combustor of a gas turbine, comprising: a combustion chamber in which mixture of air and fuel is combusted; a flow sleeve defining an air path to provide air flow to the combustion chamber; and one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.
 2. The combustor of claim 1, wherein the one or more impingement holes and a shell volume of the combustor forms a Helmholtz resonator tuned to the damping frequency.
 3. The combustor of claim 1, wherein at least one of the one or more impingement holes is disposed at an anti-node location within the combustor.
 4. The combustor of claim 1, wherein the one or more impingement holes are cylindrical.
 5. The combustor of claim 1, wherein the one or more impingement holes are polygonal.
 6. The combustor of claim 1, wherein the one or more impingement holes have different shapes.
 7. The combustor of claim 1, wherein the one or more impingement holes have different sizes.
 8. A resonator in a combustor of a gas turbine, comprising: a flow sleeve defining an air path to provide air flow to a combustion chamber of the combustor; and one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.
 9. The resonator of claim 8, wherein the one or more impingement holes and a shell volume of the combustor forms a Helmholtz resonator tuned to the damping frequency.
 10. The resonator of claim 8, wherein at least one of the one or more impingement holes is disposed at an anti-node location within the combustor.
 11. The resonator of claim 8, wherein the one or more impingement holes are cylindrical.
 12. The resonator of claim 8, wherein the one or more impingement holes are polygonal.
 13. The resonator of claim 8, wherein the one or more impingement holes have different shapes.
 14. The resonator of claim 8, wherein the one or more impingement holes have different sizes.
 15. A method of damping acoustic frequencies in a combustor of a gas turbine, comprising the steps of: providing air flow to a combustion chamber through an air path defined by a flow sleeve to form an air and fuel mixture in the combustion chamber; combusting the air and fuel mixture in the combustion chamber; and generating at least one damping frequency via one or more impingement holes disposed on the flow sleeve tuned to the at least one damping frequency to damp acoustic frequencies generated by the combusting.
 16. The method of claim 15, wherein the one or more impingement holes and a shell volume of the combustor forms a Helmholtz resonator tuned to the damping frequency.
 17. The method of claim 15, wherein at least one of the one or more impingement holes is disposed at an anti-node location within the combustor.
 18. The method of claim 15, wherein the one or more impingement holes have different shapes.
 19. The method of claim 15, wherein the one or more impingement holes have different sizes.
 20. The method of claim 15, wherein the one or more impingement holes are cylindrical or polygonal. 